1. Field of the Invention
The present invention generally relates to an actuator of a planar movement type, and more particularly, to an actuator that is incorporated into a mouse used with a personal computer or an operating unit of an audio device or a navigation device, and stimulates the tactile sensation of an operator (a user) so as to transmit certain information to the operator.
2. Description of the Related Art
There has been a type of actuator that has coils each facing a magnet placed on a flat surface, and controls the current to be supplied to the coils, so as to cause a component to move in a plane. Such an actuator can be a novel device for transmitting various kinds of information from a computer to an operator. For example, such an actuator can be incorporated into a mouse that is normally used with a personal computer.
Conventionally, a mouse has been used only as an input device for inputting information from an operator to a computer. However, a mouse containing the above actuator may vibrate in accordance with a signal transmitted from a computer, so as to stimulate the tactile sensation of a finger of the operator, for example. In this manner, the mouse can transmit various kinds of information to the operator. A conventional mouse is a unidirectional interface that works only from an operator to a computer. A mouse containing the above described actuator can serve as a bidirectional machine-man interface between a computer and an operator.
Japanese Unexamined Patent Publication No. 2003-189579 discloses a specific example of an actuator of the above described planar movement type. This actuator includes four magnets that are placed on a flat surface and are in close contact with one another, and four coils that face the respective magnets at predetermined distances and are capable of moving in a plane. When a current is supplied to the coils, a magnetic field is generated in the surrounding area of the coils, and a thrust force is generated to cause the coils to move in a plane by virtue of the electromagnetic force acting on the magnets. A tactile sensation stimulating member (a moving piece) for stimulating a finger of the operator is fixed to the side of the coils.
However, Japanese Unexamined Patent Publication No. 2003-189579 does not disclose a specific example case where the actuator is incorporated into a device such as a mouse, and does not suggest the use of the actuator in an actual product. Furthermore, the disclosed actuator has four coils on the moving end. Cables for supplying current need to be connected to the coils, and a circuit for controlling the current to be supplied to the four coils is also necessary. With those requirements being satisfied, the tactile sensation stimulating member fixed to the coils is moved in a plane (sliding movement) so as to stimulate the tactile sensation of a finger of the operator.
In the actuator disclosed in Japanese Unexamined Patent Publication No. 2003-189579, the coils move in a sliding manner, while dragging the cables. Accordingly, an excessively large thrust force is required. As the cables are dragged, a tension force is also generated on the side of the coils. This results in poor responsiveness. Furthermore, to cause the tactile sensation stimulating member to move in a plane, it is necessary to place a magnet on the entire surface (entire area) on which the coils having the tactile sensation stimulating member fixed thereto are to move. Therefore, it is necessary to prepare a magnet that is large for the area in which the tactile sensation stimulating member is to slide.
As described above, the actuator disclosed in Japanese Unexamined Patent Publication No. 2003-189579 has cables connected to the four coils on the moving end, and a circuit or the like for controlling the current application to the coils. As a result, the actuator tends to become a complicated, large-sized structure. Furthermore, it is necessary to place a magnet on the entire movement area of the coils, which also adds to the size of the actuator. As described above, the actuator disclosed in Japanese Unexamined Patent Publication No. 2003-189579 cannot be readily made smaller and tends to be a large-sized structure, and the components surrounding the actuator are also complicated and costly.